Thermal bath systems and thermally-conductive particulate thermal bath media and methods

ABSTRACT

Thermally-conductive laboratory bath media can be used to replace conventional wet media or dry solid blocks in existing thermal baths for heating or cooling samples with advantageous maintenance and microbial control benefits. The media is typically in the form of metallic or metallic-coated pellets that have rounded edges, hardened surface, a smooth polished finish, and are sized small for efficient thermal communication between pellets and samples. Laboratory bath improvements are disclosed with various advanced controls and adaptations for thermal control as well as infection control.

CROSS REFERENCES TO RELATED APPLICATION

The present application claims the benefit of prior filed U.S.Provisional Application Ser. No. 61/068,505, filed Mar. 7, 2008. By thisreference, the full disclosure, including the claims and drawings, ofU.S. provisional application Ser. No. 61/068,505 is incorporated hereinas though now set forth in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to thermal instrument baths. Moreparticularly, it especially relates to laboratory thermal baths andmedia for use therein to provide instrument maintenance and microbialcontamination control benefits.

2. Related Art

Laboratory thermal baths such as water baths and dry blocks arewell-established laboratory instruments for heating or cooling objects,vessels, or samples contained therein. Laboratory thermal baths comprisea thermal source, a temperature control unit, power source, insulation,and a tub to contain wet or dry thermal tub media. Thermal bath mediasuch as water or drilled out aluminum blocks have become a standardpractice in the laboratory.

One drawback to the present thermal bath media is that laboratorythermal baths are generally set at temperatures ideal for biologicalactivity, and therefore can promote the growth of invadingmicroorganisms on or within the media, including bacteria, yeast, fungi,and virus. This can place laboratory personnel at risk, compromiselaboratory supplies and equipment, jeopardize sterile operations, andrequire substantial routine instrument cleaning and maintenance. Wetthermal bath media, in particular water, is usually treated withantibiotic agents to prevent the initiation and persistence ofcontamination. However, these agents are impermanent, and withoutrigorous maintenance and regular renewal, they become less effective.Moreover, these agents can contribute to the formation of antibioticresistant biofilms. Such biofilms comprised of Escherichia coli,staphylococcus, or other microorganisms responsible fordifficult-to-treat infections in humans, pose a significant risk topersonnel and patients in laboratories and healthcare facilities.Furthermore, objects or capped or uncapped vessels containing samplesthat are placed into the water of the laboratory thermal bath are proneto tipping over and floating. Such events can lead to the contaminationor destruction of costly samples or sample contamination of the thermalbath and the laboratory. Moreover, thermal baths require frequent waterreplenishment and routine cleaning and maintenance, which can betime-consuming and costly.

Conventional dry thermal bath media reduce risks associated with waterbut have several additional drawbacks. In particular, solid aluminumblock systems limit the vessels that can be used to the size and shapeof the drilled-out receptacles in their bodies. Laboratory vessels dueto their unique size or shape usually necessitate the purchase ofnumerous aluminum blocks or the costly production of custom aluminumblock systems. Drawbacks to considering the use of more particulate drythermal bath media include performance challenges to minimizing thebioburden of the bath and optimizing the ability to support bathedobjects in an optimally stable position, while also providing effectivethermal transfer properties. The characteristics of particulate matterimpact the raw material cost as well as the cost and ease of using,handling, and processing the particulate matter for any particularapplication.

Many other objects and advantages will be evident to one of ordinaryskill in the art. In view of the further descriptions herein, especiallyconsidered in light of the prior art, it is therefore yet another objectof the present invention to improve upon, and overcome the obstacles ofthe prior art.

BRIEF SUMMARY OF THE INVENTION

The present invention provides thermal bath media capable of maintaininga relatively constant temperature, having optimal shape and size, andmaintenance and contamination control benefits. Central to many aspectsof the present invention is thermally-conductive particulate mediadistinguished from conventional thermal bath media. Some of the mostfavorable qualities of the thermally-conductive particulate media isappreciated with media in the form of smooth, oblong pellets havingtheir widest dimension between two and thirty millimeters, wherein saidmaterials are capable of providing thermal transfer when used instandard laboratory thermal bath. In particular, thethermally-conductive pellets are non-granular and not jagged so as notto pierce or puncture objects inserted into them, and are moisture andgas impermeable to prevent the harboring of contaminants, and aresufficiently smooth, stiff and incompressible, and in some instances aresufficiently elliptical but noncircular in at least one cross-section topermit easy insertion of vessels to promote efficient thermal transfer.The media may comprise pellets having a mixture of uniform ornon-uniform shapes and sizes.

The materials of the thermally-conductive particulate media can be ametal, preferably aluminum, silver, or copper, or a plastic, orgraphite, or the like, typically shaped like pea gravel orslightly-flattened jelly-filled doughnuts. The materials can be moldedor can be in the form of raw manufacturing material. The materials cancomprise a polished, plated, or otherwise coated surface to provide adesired finish. The pellets may comprise an outer surface and a core,wherein the outer surface material is different from the core materialsor the core may be substantially hollow.

The materials of the thermally-conductive pellets are dry and naturallymore resistant to microbial growth and than water and therefore lesslikely to harbor and contribute to transmitting microorganisms in thelaboratory. Microbial growth can be further diminished by autoclaving orby routinely applying antimicrobial agents such as fungicides,algaecides virucides, and bactericides to the thermally-conductivepellets. Such antimicrobial agents can be permanently incorporated intothe thermally-conductive pellets or otherwise onto thethermally-conductive pellets as a coating. Such coatings can preventhazardous biofilm formation and produce a microbial contaminationbarrier. Examples of antimicrobial coatings include solutions comprisedof ionic silver, ionic copper, or any permanent or semi-permanentdisinfectant.

A further advantage of the thermally-conductive pellets hereof overconventional dry thermal bath media comprised of drilled out aluminumblocks is the ability of the pellets to conform to varied sizes andshapes of vessels placed in the laboratory thermal tub. Thethermally-conductive pellets fill around the vessel providing sufficientthermal communication between the pellets and the vessel, therebyallowing the vessel and its contained specimen to reach the intendedtemperature.

Embodiments of various other aspects of the present invention alsoinclude a thermal control system comprising a laboratory thermal bathand media of thermally-conductive pellets contained in said bath and amethod for inserting sample vessels into the media in thermalcommunication with the bath.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially-cross-sectional schematic representation of onepreferred embodiment of a thermal bath system (20) according to theteachings of the present invention.

FIG. 2 is a side view of a spherical thermally-conductive pellet (41) ofcertain embodiments of the present invention.

FIG. 3 is a side perspective view of a cylindrically-shapedthermally-conductive pellet (42) of certain embodiments of the presentinvention.

FIG. 4 is a side view of a prolately-shaped thermally-conductive pellet(43) of certain embodiments of the present invention.

FIG. 5 is a perspective view of an oblately-shaped thermally-conductivepellet (44) of certain embodiments of the present invention.

FIG. 6 is a perspective view of five sample pellets (45-49) representinga particularly preferred embodiment of oblong variations of pellets (40)of the present invention.

FIG. 7 is an orthogonal view of the pellets (45-49) of FIG. 6.

FIG. 8 is a perspective cross-sectional view of a homogenous variationof pellet (41) of certain embodiments of the present invention, which isrepresentative of homogenous variations of each differently-shapedembodiment (41-49) of thermally-conductive pellets (40).

FIG. 9 is a perspective cross-sectional view of a hollow variation (41′)of pellet (41) of certain embodiments of the present invention, which isrepresentative of hollow variations of each differently-shapedembodiment (41-49) of thermally-conductive pellets (40).

FIG. 10 is a perspective cross-sectional view of adifferentially-composed version (41″) of pellet (41) of certainembodiments of the present invention, having different surface and corematerials, which is representative of differentially-composed variationsof each differently-shaped embodiment (41-49) of thermally-conductivepellets (40).

FIG. 11 is a flow chart of a preferred process of usingthermally-conductive pellets (40) in a bath system (20) of certainembodiments of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to preferred embodiments in more detail, FIG. 1 shows apartially-cross-sectional schematic representation of a thermal bathsystem (20) according to the teachings of the present invention. On thebasic level, laboratory thermal bath system (20) comprises manycomponents similar to those of conventional laboratory thermal bathsystems—namely a tub (30), a thermal source (32), power source (34), atemperature control unit (36), and thermal insulation (38). Conventionallaboratory thermal baths such as water baths and dry blocks arewell-established laboratory instruments for heating or cooling objects,vessels, or samples contained therein, and their uses have becomestandard practices in the laboratory. Hence, as will be evident to thoseof ordinary skill in the art, various alternative embodiments of thecertain aspects of the present invention can be implemented by useand/or modification of virtually any conventional laboratory thermalbath systems and their components. Such conventional laboratory thermalbaths can be obtained from numerous manufacturers through a variety ofsources—Fisher Scientific, VWR Scientific, Neslab, Tecam, and AppliedThermal Control, to name a few.

Thermal bath system (20) of FIG. 1 combines such conventional elementstogether with particulate thermally-conductive media (40) and,preferably, a disinfectant (60), to provide an overall laboratorythermal bath system (20) that can be employed to statically support andcontrol the temperature of specimens such as sample vessel (50). The tub(30) is a conventional tub that is typically employed to contain liquidthermal tub media, although modifications or substitutions may be madewhen using dry media without a liquid phase, as will be evident to thoseof skill in the art. In the embodiment of FIG. 1, tub (30) is capable ofcontaining thermally-conductive particulate media (40) (as describedfurther herein). The particulate media preferably includesthermally-conductive particles (40) that are referred to herein as“pellets,” although their preferred shapes (described further herein)are typically more like pea gravel or slightly-flattened jelly-filleddoughnuts. The particulate media serves principally to communicatethermal energy between thermal source (32) and specimen vessel (50). Theparticulate nature of media (40) secondarily serves to support one ormore vessel(s) (50) in a static orientation within media (40). Suchstatic support helps keep vessels (50) biased in an upright orientationover time rather than dumping over and risking contamination. The staticsupport of particulate media (40) also helps keep multiple vessels (50)in order within tub (30) to avoid confusion and for better tracking andthe like.

In use of the embodiment of FIG. 1 (and the alternative embodimentsdescribed herein), one or more specimen vessels (50) are inserted intothe particulate media (40) through the upper opening of the tub (30).Although the specimen vessel (50) in the illustrated embodiment is asingle test tube containing a liquid specimen, system (20) may be usedfor affecting or maintaining the thermal state of any form of specimenand/or specimen vessel for which laboratory thermal control is desired.Such specimens and/or specimen vessels may include solid objects or anyform of laboratory vessel, including (without limitation) test tubes,vials, beakers, bottles, slides, bags and the like, and the contentscontained thereby. As will be described further herein in connectionwith FIGS. 11-13, laboratory thermal bath system (20) can be employedfor heating or cooling one or more sample vessels (50) positioned in thethermally-conductive particulate media (40) contained therein.

In the embodiment of FIG. 1, the temperature of the media (40) andconsequently the specimen vessel (50) is maintained by insulation (38)in the body walls of tub (30) and by thermal source (32) typicallylocated at the base of tub (30). Although alternatives may besubstituted, thermal source (32) is powered by an electrical powersupply (34) and controlled by thermal control unit (36). The thermalcontrol unit (36) is preferably of the type having a temperature sensorand a microprocessor that can be programmed or mechanical dials that canbe electronically set and executed.

The illustrated disinfectant (60) is a spray disinfectant that isperiodically sprayed into media (40) in sufficient amounts to disinfectthe surfaces of pellets (40). When practical, the pellets (40) arestirred in the course of applying the spray disinfectant (60) in orderto increase the contact of the sprayed disinfectant with substantiallyall surfaces of the pellets (40). One particular preferred embodiment ofdisinfectant (60) is a spray bottle of silver dihydrogen citrate, abroad-spectrum antimicrobial disinfectant, which confers furtheradvantages to the thermally-conductive pellets (40). The disinfectant(60) when used to treat the thermally-conductive pellets (40) candestroy existing harmful microbes and prevent the growth and spread ofnew microbes in the laboratory. Alternative disinfectants such asbleach, alcohols, ammonium derivatives, or others can be substitutedwith corresponding properties and benefits. For each alternative of thesprayed form of disinfectant (60), care is taken to ensure that thedisinfectant (60) does not enter within the vessel (50), in order toavoid deleterious affects on the specimen therein.

Other alternatives for certain embodiments of the present inventioninclude forms of disinfectant (60) that are not spray disinfectants. Forinstance, in embodiments of the invention when the spray character isnot critical, disinfectant (60) may be in the form of disinfectantfilms, layers, coatings or impregnations that are either integral withpellets (40) or otherwise disposed in contact with the outer surfaces ofpellets (40), or may be in the form of process controls such as hightemperature treatment, autoclaving, washing, or mechanical treatment.One particularly preferred washing system is a flow-through system thatdisinfects pellets (40) by circulating a liquid disinfectant through themedia (40) while the media (40) is in its operative place within tub(30). Variations on such flow-through systems can be adapted to utilizesteam, ethylene oxide (EtO) or other gaseous disinfectants as well,although some additional adaptations will be required to handle the gas,as will be evident to those of skill in the art. Many other alternativedisinfectants will be evident to those of skill in the art, withcorresponding benefits and detractions from the foregoing embodiments.

With reference to FIG. 2 through FIG. 7, variously-shaped alternativeembodiments (41-49) of thermally-conductive pellets (40) havesubstantially rounded edges and hardened surfaces with a smooth polishedfinish. The rounded edges and polished surfaces of pellets (41-49) makethe pellets smooth and are each adaptations to ensure that, when samplevessels (50) are placed into the tub (30) to be warmed or cooled orwhenever the vessels (50) are manually moved around within tub (30),adjacent pellets (40) exert minimal friction against each other. Hence,the smooth pellets (40) move fluidly relative to each other to surroundthe vessel (50) with minimal frictional resistance and withoutsignificantly risking scratching of the surfaces of the vessels (50),which are typically glass or plastic surfaces. The thermally-conductivepellets (41-49), when used as media (40) in a thermal tub (30), fillsufficiently deep so that vessels (50) placed into the tub (30) aresufficiently submerged in the media (40). When tub (30) is so filledwith particulate media (40), the sample vessels (50) are held in placeand in position without the need for a further holding device, such asstationary or floating racks.

The different shapes of pellets (41-49) provide different benefits anddetractions of the various embodiments that can be used for particulatemedia (40) of the present invention. Some aspects of the presentinvention are embodied with the use of oblong pellets, such as isdescribed further herein. Although a spherical thermally-conductivepellet (41) as shown in FIG. 2 is not oblong, some aspects of thepresent invention can be appreciated with the use of pellets (41) havinga spherical shape, either alone or in combination with oblong pellets(40). Likewise, although a cylindrical thermally-conductive pellet (42)as shown in FIG. 3 has some edges (42′ & 42″) that are not rounded, itssidewall (42′″) is rounded, and some aspects of the present inventioncan be appreciated with the use of pellets (42) that have somenon-rounded edges (42′ & 42″), either alone or in combination withpellets (40) that have all their surfaces and edges rounded.

It may be that surface descriptions such as “rounded,” “polished” and“smooth” may be thought of as relative terms. It should be understoodthat pellets (40) can have immaterial surface imperfections (such as theimperfections visible in FIGS. 6 & 7) while still being considered“rounded” and “smooth.” All of the surfaces and edges of the pellets(45-49) shown in FIGS. 6 and 7 are considered rounded and smooth despiteall the imperfections visible therein. While the “polished” term refersto the way the surface of a pellet (40) is processed, all the surfacesof the pellets (45-49) shown in FIGS. 6 and 7 are polished. It is alsonoted that concavities in the surface of a pellet (40), such as thecentral dimple (47′) of the middle pellet (47) in FIG. 6, are immaterialto smoothness of the pellet (40). In an attempt to quantify the size ofimmaterial surface protrusions from an otherwise smooth surface, it isthought that surface protrusions having protruding dimensions (i.e., theradial extent of the protrusion) that are less than a third of thethinnest dimension (t) of an otherwise smooth pellet (40) areimmaterial. Despite such protruding imperfections, it is thought thatprotrusions of such sizes would still be smooth.

The pellets that make up at least the bulk (i.e., the majority byvolume) if not the entirety of particulate media (40) in tub (30) arepreferably oblong pellets. Referring particularly to the pellets (43 &44) of FIGS. 4 & 5, the shape of oblong pellets can be betterunderstood. Such pellets are referred to as “oblong” in the sense thateach pellet's (43, 44) shortest through dimension (its “thinnestdimension” or “t”) is significantly shorter than its longest throughdimension (its “widest dimension” or “w”). The prolately-shaped pellet(43) of FIG. 4 more accurately has the shape of a vertical cylinder withhemi-spherically rounded ends (43′ & 43″); the thinnest dimension (t) ofpellet 43 being the thickness of the cylinder, and the widest dimension(w) being the distance between the ends (43′ & 43″). Theprolately-shaped pellet (44) of FIG. 5 more accurately has the shape ofa prolate sphere (or an ellipsoid, much like the globe of the Earth)with symmetrically-truncated polar ends (44′ & 44″); the widestdimension (w) of pellet (44) being the equatorial diameter of theprolate sphere, and the thinnest dimension (t) being the distancebetween the truncated polar ends (43′ & 43″). Both the prolately-shapedpellet (43) of FIG. 4 and the oblately-shaped pellet (44) of FIG. 5 areoblong.

Preferably, an oblong pellet of particulate media (40) has a thinnestdimension (t) that is about half of its widest dimension (w) or,preferably, more than 25% and less than 75% of the widest dimension (w).The same oblong character can also be seen in each of the pellets(45-49) of FIGS. 6 & 7, which are all preferred oblong variations(45-49) of pellets (40).

FIGS. 6 & 7 show five representative sample pellets (45-49) representinga particularly preferred embodiment of the preferred oblong variationsof pellets (40) of the present invention. As will be elaborated furtherherein, the pellets (45-49) are preferably formed by polishing metalpellets or shot (preferably formed of aluminum) acquired in raw formfrom metal fabricators. Referring to the preferred embodiments of FIG.1, such polished pellets (represented by samples 45-49 in FIGS. 6 & 7)serve as the pellets (40) for thermal bath system (20) in presentlypreferred embodiments. Because of the shape, thermal conductivity andsmall size of such pellets (45-49), the particulate media (40) allowsfor efficient thermal communication by maximizing surface-to-surfacecontact between the pellets (40) and both the introduced specimenvessel(s) (50) as well as the thermal element (32).

Although oblong pellets (40) according to some aspects of the presentinvention may have a widest dimension (w) as large as thirtymillimeters, the bulk of the pellets (40) of the most preferredembodiment have widest dimensions (w) of less than ten millimeters andpreferably more than two millimeters.

In practice, in order to manage costs, the thermally-conductive pellets(40) of preferred embodiments are formed from irregularly-shapedparticles of raw material, preferably with rounded and smooth surfaces.Even though such raw material is available with fairly smooth surfacesin its raw state, for optimal use of the present invention, it should bepolished smooth in order to minimize friction between adjacent pellets(40) in a bath system (20). Pellets (40) are made of thermallyconductive raw material, preferably a solid metal and most preferablyaluminum or an aluminum alloy. Such raw material is preferably acquiredfrom metal manufacturing plants in the form of pellets or shot, whichmay also be referred to as “granny pea,” “mini pea” or “granulatedparticle ingot,” and can be obtained at high purity, preferably ofgreater than 99% purity. The raw material is preferably not molded, inorder to minimize cost of manufacture and/or purchase. Any standardsmall metal parts finishing equipment such as a vibratory bowl orvibratory tub can be used to polish the raw material with or withoutabrasives to achieve the desired polished surface characteristics of thepreferred embodiments.

The performance characteristics of the resulting thermally-conductivepellets (40) are favorable attributes of the preferred embodiments. Notonly do the resulting pellets (40) allow for high thermal conductivityand thermal retention when used in system (20), but pellets (40) alsoprovide a balance of mechanical fluidity and support. The balance ofmechanical fluidity and support allows vessels (50) to be readilyinserted into the particulate media (40) [or the multi-phase media (71),when used in any particular embodiment] and thereafter held in place ina static position due to the mechanical interaction between theparticulate media (40). A favorable aspect of the particulate media (40)resulting from this preferred method is that the bulk (i.e., themajority by volume) of the pellets are oblong in shape, which enhancesthe overall fluidity of the resulting media (40). Moreover, the pellets(40) of preferred embodiments are microbial resistant and are bothmoisture and gas impermeable.

Although some embodiments use pellets (40) of uniform sizes, otherpreferred embodiments use pellets (40) of mixed sizes and shapes, whichtypically allows for improved fluidity and thermal conductivity due tothe distribution of smaller pellets with respect to larger pellets in amixture. Irregularly shaped thermally-conductive pellets (40) preferablyhave widest dimensions (w) in the range of 2-10 millimeters andpreferably take on an overall form of smooth symmetrical ornonsymmetrical ellipsoids, such as in a blend from which the fiverepresentative samples of FIGS. 6 & 7 have been sampled.

Despite the general preference to use rounded pellets that have beenpolished smooth, some aspects of the invention may still be appreciatedwith less-preferred alternative forms for pellets (40), that may includerough, jagged, uneven, rutted, bumpy, pitted, and etched forms,including polygons such as cubes, cones, pyramids, and cylinders, ortwists, or rings, or various combinations of these or other forms.

FIG. 8 shows a solid, homogenous pellet (41) as a representativecomparator for any of the solid, homogenous pellets (40-49) describedabove with reference to FIGS. 1-8. As a homogenous pellet (41), theouter surface (41 a) is of the same composition as the core (41 b) ofthe pellet (41) shown in FIG. 8, the composition beingthermally-conductive and preferably a solid metal. The specificcomposition of the thermally-conductive material in preferredembodiments is most preferably aluminum or an alloy of aluminum. Inalternative embodiments, copper, graphite, cobalt oxide or otherthermally-conductive materials may alternately be used as thethermally-conductive raw material for pellets (40), as will be known tothose of skill in the art. Alternative materials such as lightweightthermally-conductive plastics, epoxies and the like are particularlyadvantageous alternatives for use in applications where either minimalweight is desired and/or where there is a desire to minimize electricalconductivity through the particulate thermal media (40) within tub (30).

With reference to FIGS. 9 & 10, certain additional advantages areobtained with alternative embodiments that employ pellets (40) havinghollow and/or differential composition, respectively. FIG. 9 moreparticularly shows a representative thermally-conductive pellet (41)having a thermally conductive outer surface (41 a′) surrounding asubstantially hollow core (41 b′). FIG. 10 shows a representativethermally-conductive pellet (41) having a thermally conductive outersurface (41 a″) surrounding a less dense or less conductive core (41b″). The outer surface (41 a″) can be made from any sufficientlythermally-conductive material and is composed of a different materialthan the material of inner core (41 b″), which can be made from anyrigid or non-rigid material such as ceramic, plastic, foam, water, gelor other semi-liquid or liquid. Due to the difference between thethermal conductivity and/or density properties of the surface (41 a″)and the core (41 b″) of representative pellet (41″), pellet (41″) isreferred to as having “differential composition”. As will be understoodby those of skill in the art, any of the variously shaped pellets(40-49) described in this application can be made of hollow ordifferential composition just as pellet (41′) is hollow and pellet (41″)has differential composition.

With reference again to FIG. 1, in some preferred embodiments, tub (30)is filled with a multi-phase media (71), which is a multi-phasevariation of thermally-conductive media. Multi-phase media (71) is“multi-phase” in that it is a combination of particulate media (40) anda fluid (70), preferably a liquid. Alternate embodiments of the fluid(70) of multi-phase media (71) include semi-liquids, gasses or vapors,or combinations thereof or combinations with liquids. Preferably,though, multi-phase media (71) includes particulate thermal media (40)[most preferably like oblong pellets (45-49)] together with water orother liquid media (70). In such embodiments, the fluid media (70) isgenerally included to help enhance the thermal properties of the thermalmedia (71). Liquid media (70) may also consist of or include lubricantsand/or disinfectants (or the like) for the purposes of increasingfluidity and microbial control, respectively, of the media (71) withintub (30).

With embodiments relating to multi-phase media (71) that include liquidfluid media (70), the liquid portion (70) of the thermal media (71)generally fills the interstitial spaces (40′) between the pellets (40),at least up to the level of the upper surface (70′) of liquid media(70). For embodiments with liquid media (70), the level of the uppersurface (referred to as the “fill level”) (70′) of liquid media (70)preferably covers substantially all of the particulate media (40), suchas illustrated in FIG. 1. However, lower liquid fill levels may also beused as desired. For instance, the fill level of liquid media (70) canbe limited to a low level (70″) (shown in dashed line) that covers thethermal element 32 but does not cover all the particulate media (40). Atsuch a low fill level (70″), thermally-conductive liquid fluid media(70) helps facilitate heat transfer between thermal element (32) andparticulate media (40) without wetting as much of the particulate media(40) and/or the specimen vessel(s) (50).

Although not essential to all aspects of the present invention, somepreferred embodiments also utilize an impeller (75) (or a tumbler or thelike) to stir or agitate the beads (40) and cause them to be spaciallyredistributed within tub (30), thereby increasing the rate of heattransfer within media (40) relative to thermal source (32). Operation ofimpeller (75) is especially beneficial to rapidly change (or “ramp up”or “boost”) the temperature of the particulate media (40) near the topof tub (30), such as may be desired during prep time before vessels (50)are placed in media (40). However, as is shown in FIG. 1, impeller (75)is preferably disposed at a position within tub (30) such that impeller(75) is not likely to physically engage vessel(s) (50) during itsoperation. As a substitute or augmentation for impeller (75),alternative devices or systems for stirring or otherwise spaciallyredistributing pellets (40) and/or for rapidly boosting or changing thetemperature of particulate media (40) will be evident to those of skillin the art. A heated air blower (such as a hair blow dryer) positionedto blow through the media (40) is one particular example of such analternative embodiment for use to rapidly boost the temperature ofparticulate media (40), particularly for when media (40) is used dry.Systems for circulating super-heated steam through dry particulate media(40) can also be used to serve both the boost function as well as thesterilization purpose described elsewhere herein. Although not shown inFIG. 1, those of ordinary skill in the art will understand that impeller(75) (or its alternatives or equivalents) has an associated motor andmotor controls for turning the shaft (76) to operatively rotate impeller(75).

Despite the benefits of such multi-phase media (71), other aspects ofthe present invention can be appreciated without using any fluid portion(70) of the thermal media in tub (30), in which cases the particulatemedia (40) is dry particulate media. By using dry particulate media(40), many of the hazards and maintenance burdens of using water bathscan be avoided.

While numerous variations on the size, shape and composition of theparticulate media (40) and/or multi-phase media (71) have been describedabove, it should be understood by those skilled in the art having thebenefit of this disclosure that the drawings and detailed descriptionherein are to be regarded in an illustrative rather than a restrictivemanner, and are not intended to limit the invention to the particularforms and examples disclosed. On the contrary, the invention includesany further modifications, changes, rearrangements, substitutions,alternatives, design choices, and embodiments apparent to those ofordinary skill in the art, without departing from the spirit and scopeof this invention, as defined by the claims that may appear with thisapplication or may be later added or amended. Thus, although theforegoing embodiments have been described, those of ordinary skill inthe art will recognize many possible additional alternatives. Forexample, although it is preferred that at least the bulk of theparticulate media (40) consist of a blend or mixture of one or more ofthe embodiments described herein, it may be beneficial to useparticulate media (40) and/or multi-phase media (71) that includesblends or mixtures of the various embodiments that have been describedtogether with other materials that have not been remotely described oreven suggested. In any case, all substantially equivalent forms ofparticulate thermal media should be considered within the scope of thethermal media of this invention to the extent that the claims do notpreclude as much when properly construed.

While much of the above descriptions describe preferred forms ofparticulate media (40) and production and preparation of the same, FIG.11 shows a flow chart of a preferred process of using thethermally-conductive particulate media (40) in a bath system (20) ofcertain preferred embodiments of the present invention. The first step(81) of such process is to prepare the thermal bath system (20) inaccordance with the foregoing descriptions, filling tub (30) withappropriate particulate thermally-conductive media (40) or multi-phasemedia (71) to the desired fill levels. After preparing and/or obtaininga thermal bath system (20) with thermally-conductive pellets (40) ofappropriate character according to the teachings of the presentinvention, a user (or an automated control) would then proceed to thefollowing steps (82-86).

Referring to the flow chart in FIG. 11, the second step (82) of thepreferred process involves setting the system (20) to the desiredtemperature and activating the thermal controls to maintain as much,thereby bringing the thermal media within tub (30) to the desiredtemperature, whether it be above or below ambient. Such setting andactivating step (82) involves use of thermal source (32), power source(34), and temperature control unit (36) in the conventional manner, withthe aid of thermal insulation (38). To shorten the time to reach thedesired temperature, it may be appropriate to stir the particulate media(40) after 10-30 min and/or periodically. Once stirred, the temperatureof the particulate media (40) should be allowed to equilibrate for 15-60minutes.

The next step (83) of positioning sample vessel(s) (50) in the thermalmedia (40, 71) is generally performed manually and is enabled by thefluidity of the particulate media (40). As is conventional with waterbaths, the objects or specimen vessel(s) (50) should be placed such thatthey are substantially immersed in media (40) without being immersed sofar as to risk contamination through any upper opening in the vessel(s)(50), particularly when a liquid (70) is used with particulate media(40). Once appropriately placed, the vessel(s) (or objects) (50) canthen remain in place without a rack and are left to incubate (i.e., toremain at the set temperature) for whatever period of time is desired.After the desired incubation time has been achieved, the vessel(s) (50)are removed (typically by hand) from system (20) at the bottom step (85)for further processing outside of system (20).

The final step (86) before reusing the system (20) is to clean orsterilize the thermally conductive media (40, 71) using techniquesmentioned elsewhere herein or as will be evident to those of skill inthe art. The final step (86) also preferably involves briefly agitatingthe particulate media (40) both after the last use and before the nextuse of system (20). While this step (86) is shown serially between thesample removal step (85) and the restart step (82), it should beunderstood that sterilization (86) (and other steps) may be omittedentirely or may be performed in a different sequence. This isparticularly the case with the sterilization and/or cleaning step (86)as alternative cleaning and/or sterilization processes may be performedduring the course of other steps (81-85) of the process, or may beomitted entirely, to the extent that bioburdens within media (40) arewithin levels required for integrity of whatever test is being conductedon vessel(s) (50).

In a particularly preferred variation of the thermal bath system (20)shown in FIG. 1, programming controls are included with temperaturecontrol unit (36) to also control the staged and timed operation of eachstep (81-86) of the method of FIG. 11. In such variation, control unit(36) includes one or more timers to automatically activate parts ofsteps (81-86) at scheduled or anticipated times during the day andduring each cycle of using system (20). Particularly, automated cleaningand/or sterilizing variations of step (86) are automatically activatedby control unit (36) at scheduled times after and before each shift inwhich the thermal bath system (20) has been or is likely to be used, inorder to minimize microbial contamination in tub (30). Likewise, thethermal source (32) and/or the impeller (75) are activated by controlunit (36) at scheduled or anticipated times before each shift in whichthe thermal bath system (20) is likely to be used, in order to minimizecostly staff and/or equipment downtime (and potentially costly waste ofspecimens) while waiting for the required temperature of media (40) tobe reached. Once the required temperature of media (40) is attained, asdetermined by a temperature probe or the like connected to control unit(36), automated controls in unit (36) then preferably deactivateimpeller (75) and cause a visual, auditory or electronic “READY” signalto be presented to users of system (20). Thereafter, thermal controlscontinue to maintain the temperatures in the conventional manner,allowing for a user to program the duration of the incubation time (orthe remaining incubation time) or to adjust the temperature setting ofcontrol unit (36) to any particular level at any time. Once theprogrammed incubation time is completed, the automated controls of unit(36) preferably also include provision for presenting an “INCUBATIONCOMPLETE” visual, auditory or electronic signal to indicate that thedesired incubation period is completed, while also discontinuingoperation of thermal source (32) at the appropriate time.

In certain embodiments, such automated controls of control unit (36) mayalso be coupled to automated specimen racks in order to cause vessel(s)(50) to be inserted into and/or removed from media (40) in accordancewith a pre-programmed sequence, in order to provide a fully automatedsystem (20).

In broad embodiment, the present invention is thermal bath media ofthermally-conductive particulate media of any shape or material whichcan be used to replace conventional wet or dry media in existinglaboratory thermal bath for transferring thermal energy to objectsplaced within. The present invention also envisions laboratory thermalbath optimally designed for use with thermally-conductive particulatemedia. Such laboratory thermal baths can comprise tub designs thatprovide optimal containment of the thermal bath media, optimal thermaltransfer properties, and optimal design for ease-of-use, adaptation torobotic platforms and sterile laboratory applications.

While the foregoing written description enables one of ordinary skill tomake and use what is considered presently to be the best mode thereof,those of ordinary skill will understand and appreciate the existence ofvariations, combinations, and equivalents of the specific embodiment,method, and examples herein. The invention should therefore not belimited by the above described embodiment, method, and examples, but byall embodiments and methods within the scope and spirit of the inventionas claimed. It is intended instead that any claims with thisapplication, or any claims that may be added or amended, be interpretedto embrace all further modifications, changes, rearrangements,substitutions, alternatives, design choices, and embodiments that may beevident to those of skill in the art. Although the foregoing embodimentsare the most preferred at present, those of ordinary skill in the artwill recognize many possible alternatives. For example, it may bepossible to find another material that works better than the particularswe have discussed. In any case, all substantially equivalent systems,articles and methods should be considered within the scope of thepresent invention.

CROSS REFERENCES TO RELATED APPLICATION

The present application claims the benefit of prior filed U.S.Provisional Application Ser. No. 61/068,505, filed Mar. 7, 2008. By thisreference, the full disclosure, including the claims and drawings, ofU.S. provisional application Ser. No. 61/068,505 is incorporated hereinas though now set forth in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to thermal instrument baths. Moreparticularly, it especially relates to laboratory thermal baths andmedia for use therein to provide instrument maintenance and microbialcontamination control benefits.

2. Related Art

Laboratory thermal baths such as water baths and dry blocks arewell-established laboratory instruments for heating or cooling objects,vessels, or samples contained therein. Laboratory thermal baths comprisea thermal source, a temperature control unit, power source, insulation,and a tub to contain wet or dry thermal tub media. Thermal bath mediasuch as water or drilled out aluminum blocks have become a standardpractice in the laboratory.

One drawback to the present thermal bath media is that laboratorythermal baths are generally set at temperatures ideal for biologicalactivity, and therefore can promote the growth of invadingmicroorganisms on or within the media, including bacteria, yeast, fungi,and virus. This can place laboratory personnel at risk, compromiselaboratory supplies and equipment, jeopardize sterile operations, andrequire substantial routine instrument cleaning and maintenance. Wetthermal bath media, in particular water, is usually treated withantibiotic agents to prevent the initiation and persistence ofcontamination. However, these agents are impermanent, and withoutrigorous maintenance and regular renewal, they become less effective.Moreover, these agents can contribute to the formation of antibioticresistant biofilms. Such biofilms comprised of Escherichia coli,staphylococcus, or other microorganisms responsible fordifficult-to-treat infections in humans, pose a significant risk topersonnel and patients in laboratories and healthcare facilities.Furthermore, objects or capped or uncapped vessels containing samplesthat are placed into the water of the laboratory thermal bath are proneto tipping over and floating. Such events can lead to the contaminationor destruction of costly samples or sample contamination of the thermalbath and the laboratory. Moreover, thermal baths require frequent waterreplenishment and routine cleaning and maintenance, which can betime-consuming and costly.

Conventional dry thermal bath media reduce risks associated with waterbut have several additional drawbacks. In particular, solid aluminumblock systems limit the vessels that can be used to the size and shapeof the drilled-out receptacles in their bodies. Laboratory vessels dueto their unique size or shape usually necessitate the purchase ofnumerous aluminum blocks or the costly production of custom aluminumblock systems. Drawbacks to considering the use of more particulate drythermal bath media include performance challenges to minimizing thebioburden of the bath and optimizing the ability to support bathedobjects in an optimally stable position, while also providing effectivethermal transfer properties. The characteristics of particulate matterimpact the raw material cost as well as the cost and ease of using,handling, and processing the particulate matter for any particularapplication.

Many other objects and advantages will be evident to one of ordinaryskill in the art. In view of the further descriptions herein, especiallyconsidered in light of the prior art, it is therefore yet another objectof the present invention to improve upon, and overcome the obstacles ofthe prior art.

BRIEF SUMMARY OF THE INVENTION

The present invention provides thermal bath media capable of maintaininga relatively constant temperature, having optimal shape and size, andmaintenance and contamination control benefits. Central to many aspectsof the present invention is thermally-conductive particulate mediadistinguished from conventional thermal bath media. Some of the mostfavorable qualities of the thermally-conductive particulate media isappreciated with media in the form of smooth, oblong pellets havingtheir widest dimension between two and thirty millimeters, wherein saidmaterials are capable of providing thermal transfer when used instandard laboratory thermal bath. In particular, thethermally-conductive pellets are non-granular and not jagged so as notto pierce or puncture objects inserted into them, and are moisture andgas impermeable to prevent the harboring of contaminants, and aresufficiently smooth, stiff and incompressible, and in some instances aresufficiently elliptical but noncircular in at least one cross-section topermit easy insertion of vessels to promote efficient thermal transfer.The media may comprise pellets having a mixture of uniform ornon-uniform shapes and sizes.

The materials of the thermally-conductive particulate media can be ametal, preferably aluminum, silver, or copper, or a plastic, orgraphite, or the like, typically shaped like pea gravel orslightly-flattened jelly-filled doughnuts. The materials can be moldedor can be in the form of raw manufacturing material. The materials cancomprise a polished, plated, or otherwise coated surface to provide adesired finish. The pellets may comprise an outer surface and a core,wherein the outer surface material is different from the core materialsor the core may be substantially hollow.

The materials of the thermally-conductive pellets are dry and naturallymore resistant to microbial growth and than water and therefore lesslikely to harbor and contribute to transmitting microorganisms in thelaboratory. Microbial growth can be further diminished by autoclaving orby routinely applying antimicrobial agents such as fungicides,algaecides virucides, and bactericides to the thermally-conductivepellets. Such antimicrobial agents can be permanently incorporated intothe thermally-conductive pellets or otherwise onto thethermally-conductive pellets as a coating. Such coatings can preventhazardous biofilm formation and produce a microbial contaminationbarrier. Examples of antimicrobial coatings include solutions comprisedof ionic silver, ionic copper, or any permanent or semi-permanentdisinfectant.

A further advantage of the thermally-conductive pellets hereof overconventional dry thermal bath media comprised of drilled out aluminumblocks is the ability of the pellets to conform to varied sizes andshapes of vessels placed in the laboratory thermal tub. Thethermally-conductive pellets fill around the vessel providing sufficientthermal communication between the pellets and the vessel, therebyallowing the vessel and its contained specimen to reach the intendedtemperature.

Embodiments of various other aspects of the present invention alsoinclude a thermal control system comprising a laboratory thermal bathand media of thermally-conductive pellets contained in said bath and amethod for inserting sample vessels into the media in thermalcommunication with the bath.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially-cross-sectional schematic representation of onepreferred embodiment of a thermal bath system (20) according to theteachings of the present invention.

FIG. 2 is a side view of a spherical thermally-conductive pellet (41) ofcertain embodiments of the present invention.

FIG. 3 is a side perspective view of a cylindrically-shapedthermally-conductive pellet (42) of certain embodiments of the presentinvention.

FIG. 4 is a side view of a prolately-shaped thermally-conductive pellet(43) of certain embodiments of the present invention.

FIG. 5 is a perspective view of an oblately-shaped thermally-conductivepellet (44) of certain embodiments of the present invention.

FIG. 6 is a perspective view of five sample pellets (45-49) representinga particularly preferred embodiment of oblong variations of pellets (40)of the present invention.

FIG. 7 is an orthogonal view of the pellets (45-49) of FIG. 6.

FIG. 8 is a perspective cross-sectional view of a homogenous variationof pellet (41) of certain embodiments of the present invention, which isrepresentative of homogenous variations of each differently-shapedembodiment (41-49) of thermally-conductive pellets (40).

FIG. 9 is a perspective cross-sectional view of a hollow variation (41′)of pellet (41) of certain embodiments of the present invention, which isrepresentative of hollow variations of each differently-shapedembodiment (41-49) of thermally-conductive pellets (40).

FIG. 10 is a perspective cross-sectional view of adifferentially-composed version (41″) of pellet (41) of certainembodiments of the present invention, having different surface and corematerials, which is representative of differentially-composed variationsof each differently-shaped embodiment (41-49) of thermally-conductivepellets (40).

FIG. 11 is a flow chart of a preferred process of usingthermally-conductive pellets (40) in a bath system (20) of certainembodiments of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to preferred embodiments in more detail, FIG. 1 shows apartially-cross-sectional schematic representation of a thermal bathsystem (20) according to the teachings of the present invention. On thebasic level, laboratory thermal bath system (20) comprises manycomponents similar to those of conventional laboratory thermal bathsystems—namely a tub (30), a thermal source (32), power source (34), atemperature control unit (36), and thermal insulation (38). Conventionallaboratory thermal baths such as water baths and dry blocks arewell-established laboratory instruments for heating or cooling objects,vessels, or samples contained therein, and their uses have becomestandard practices in the laboratory. Hence, as will be evident to thoseof ordinary skill in the art, various alternative embodiments of thecertain aspects of the present invention can be implemented by useand/or modification of virtually any conventional laboratory thermalbath systems and their components. Such conventional laboratory thermalbaths can be obtained from numerous manufacturers through a variety ofsources—Fisher Scientific, VWR Scientific, Neslab, Tecam, and AppliedThermal Control, to name a few.

Thermal bath system (20) of FIG. 1 combines such conventional elementstogether with particulate thermally-conductive media (40) and,preferably, a disinfectant (60), to provide an overall laboratorythermal bath system (20) that can be employed to statically support andcontrol the temperature of specimens such as sample vessel (50). The tub(30) is a conventional tub that is typically employed to contain liquidthermal tub media, although modifications or substitutions may be madewhen using dry media without a liquid phase, as will be evident to thoseof skill in the art. In the embodiment of FIG. 1, tub (30) is capable ofcontaining thermally-conductive particulate media (40) (as describedfurther herein). The particulate media preferably includesthermally-conductive particles (40) that are referred to herein as“pellets,” although their preferred shapes (described further herein)are typically more like pea gravel or slightly-flattened jelly-filleddoughnuts. The particulate media serves principally to communicatethermal energy between thermal source (32) and specimen vessel (50). Theparticulate nature of media (40) secondarily serves to support one ormore vessel(s) (50) in a static orientation within media (40). Suchstatic support helps keep vessels (50) biased in an upright orientationover time rather than dumping over and risking contamination. The staticsupport of particulate media (40) also helps keep multiple vessels (50)in order within tub (30) to avoid confusion and for better tracking andthe like.

In use of the embodiment of FIG. 1 (and the alternative embodimentsdescribed herein), one or more specimen vessels (50) are inserted intothe particulate media (40) through the upper opening of the tub (30).Although the specimen vessel (50) in the illustrated embodiment is asingle test tube containing a liquid specimen, system (20) may be usedfor affecting or maintaining the thermal state of any form of specimenand/or specimen vessel for which laboratory thermal control is desired.Such specimens and/or specimen vessels may include solid objects or anyform of laboratory vessel, including (without limitation) test tubes,vials, beakers, bottles, slides, bags and the like, and the contentscontained thereby. As will be described further herein in connectionwith FIGS. 11-13, laboratory thermal bath system (20) can be employedfor heating or cooling one or more sample vessels (50) positioned in thethermally-conductive particulate media (40) contained therein.

In the embodiment of FIG. 1, the temperature of the media (40) andconsequently the specimen vessel (50) is maintained by insulation (38)in the body walls of tub (30) and by thermal source (32) typicallylocated at the base of tub (30). Although alternatives may besubstituted, thermal source (32) is powered by an electrical powersupply (34) and controlled by thermal control unit (36). The thermalcontrol unit (36) is preferably of the type having a temperature sensorand a microprocessor that can be programmed or mechanical dials that canbe electronically set and executed.

The illustrated disinfectant (60) is a spray disinfectant that isperiodically sprayed into media (40) in sufficient amounts to disinfectthe surfaces of pellets (40). When practical, the pellets (40) arestirred in the course of applying the spray disinfectant (60) in orderto increase the contact of the sprayed disinfectant with substantiallyall surfaces of the pellets (40). One particular preferred embodiment ofdisinfectant (60) is a spray bottle of silver dihydrogen citrate, abroad-spectrum antimicrobial disinfectant, which confers furtheradvantages to the thermally-conductive pellets (40). The disinfectant(60) when used to treat the thermally-conductive pellets (40) candestroy existing harmful microbes and prevent the growth and spread ofnew microbes in the laboratory. Alternative disinfectants such asbleach, alcohols, ammonium derivatives, or others can be substitutedwith corresponding properties and benefits. For each alternative of thesprayed form of disinfectant (60), care is taken to ensure that thedisinfectant (60) does not enter within the vessel (50), in order toavoid deleterious affects on the specimen therein.

Other alternatives for certain embodiments of the present inventioninclude forms of disinfectant (60) that are not spray disinfectants. Forinstance, in embodiments of the invention when the spray character isnot critical, disinfectant (60) may be in the form of disinfectantfilms, layers, coatings or impregnations that are either integral withpellets (40) or otherwise disposed in contact with the outer surfaces ofpellets (40), or may be in the form of process controls such as hightemperature treatment, autoclaving, washing, or mechanical treatment.One particularly preferred washing system is a flow-through system thatdisinfects pellets (40) by circulating a liquid disinfectant through themedia (40) while the media (40) is in its operative place within tub(30). Variations on such flow-through systems can be adapted to utilizesteam, ethylene oxide (EtO) or other gaseous disinfectants as well,although some additional adaptations will be required to handle the gas,as will be evident to those of skill in the art. Many other alternativedisinfectants will be evident to those of skill in the art, withcorresponding benefits and detractions from the foregoing embodiments.

With reference to FIG. 2 through FIG. 7, variously-shaped alternativeembodiments (41-49) of thermally-conductive pellets (40) havesubstantially rounded edges and hardened surfaces with a smooth polishedfinish. The rounded edges and polished surfaces of pellets (41-49) makethe pellets smooth and are each adaptations to ensure that, when samplevessels (50) are placed into the tub (30) to be warmed or cooled orwhenever the vessels (50) are manually moved around within tub (30),adjacent pellets (40) exert minimal friction against each other. Hence,the smooth pellets (40) move fluidly relative to each other to surroundthe vessel (50) with minimal frictional resistance and withoutsignificantly risking scratching of the surfaces of the vessels (50),which are typically glass or plastic surfaces. The thermally-conductivepellets (41-49), when used as media (40) in a thermal tub (30), fillsufficiently deep so that vessels (50) placed into the tub (30) aresufficiently submerged in the media (40). When tub (30) is so filledwith particulate media (40), the sample vessels (50) are held in placeand in position without the need for a further holding device, such asstationary or floating racks.

The different shapes of pellets (41-49) provide different benefits anddetractions of the various embodiments that can be used for particulatemedia (40) of the present invention. Some aspects of the presentinvention are embodied with the use of oblong pellets, such as isdescribed further herein. Although a spherical thermally-conductivepellet (41) as shown in FIG. 2 is not oblong, some aspects of thepresent invention can be appreciated with the use of pellets (41) havinga spherical shape, either alone or in combination with oblong pellets(40). Likewise, although a cylindrical thermally-conductive pellet (42)as shown in FIG. 3 has some edges (42′ & 42″) that are not rounded, itssidewall (42′″) is rounded, and some aspects of the present inventioncan be appreciated with the use of pellets (42) that have somenon-rounded edges (42′ & 42″), either alone or in combination withpellets (40) that have all their surfaces and edges rounded.

It may be that surface descriptions such as “rounded,” “polished” and“smooth” may be thought of as relative terms. It should be understoodthat pellets (40) can have immaterial surface imperfections (such as theimperfections visible in FIGS. 6 & 7) while still being considered“rounded” and “smooth.” All of the surfaces and edges of the pellets(45-49) shown in FIGS. 6 and 7 are considered rounded and smooth despiteall the imperfections visible therein. While the “polished” term refersto the way the surface of a pellet (40) is processed, all the surfacesof the pellets (45-49) shown in FIGS. 6 and 7 are polished. It is alsonoted that concavities in the surface of a pellet (40), such as thecentral dimple (47′) of the middle pellet (47) in FIG. 6, are immaterialto smoothness of the pellet (40). In an attempt to quantify the size ofimmaterial surface protrusions from an otherwise smooth surface, it isthought that surface protrusions having protruding dimensions (i.e., theradial extent of the protrusion) that are less than a third of thethinnest dimension (t) of an otherwise smooth pellet (40) areimmaterial. Despite such protruding imperfections, it is thought thatprotrusions of such sizes would still be smooth.

The pellets that make up at least the bulk (i.e., the majority byvolume) if not the entirety of particulate media (40) in tub (30) arepreferably oblong pellets. Referring particularly to the pellets (43 &44) of FIGS. 4 & 5, the shape of oblong pellets can be betterunderstood. Such pellets are referred to as “oblong” in the sense thateach pellet's (43, 44) shortest through dimension (its “thinnestdimension” or “t”) is significantly shorter than its longest throughdimension (its “widest dimension” or “w”). The prolately-shaped pellet(43) of FIG. 4 more accurately has the shape of a vertical cylinder withhemi-spherically rounded ends (43′ & 43″); the thinnest dimension (t) ofpellet 43 being the thickness of the cylinder, and the widest dimension(w) being the distance between the ends (43′ & 43″). Theprolately-shaped pellet (44) of FIG. 5 more accurately has the shape ofa prolate sphere (or an ellipsoid, much like the globe of the Earth)with symmetrically-truncated polar ends (44′ & 44″); the widestdimension (w) of pellet (44) being the equatorial diameter of theprolate sphere, and the thinnest dimension (t) being the distancebetween the truncated polar ends (43′ & 43″). Both the prolately-shapedpellet (43) of FIG. 4 and the oblately-shaped pellet (44) of FIG. 5 areoblong.

Preferably, an oblong pellet of particulate media (40) has a thinnestdimension (t) that is about half of its widest dimension (w) or,preferably, more than 25% and less than 75% of the widest dimension (w).The same oblong character can also be seen in each of the pellets(45-49) of FIGS. 6 & 7, which are all preferred oblong variations(45-49) of pellets (40).

FIGS. 6 & 7 show five representative sample pellets (45-49) representinga particularly preferred embodiment of the preferred oblong variationsof pellets (40) of the present invention. As will be elaborated furtherherein, the pellets (45-49) are preferably formed by polishing metalpellets or shot (preferably formed of aluminum) acquired in raw formfrom metal fabricators. Referring to the preferred embodiments of FIG.1, such polished pellets (represented by samples 45-49 in FIGS. 6 & 7)serve as the pellets (40) for thermal bath system (20) in presentlypreferred embodiments. Because of the shape, thermal conductivity andsmall size of such pellets (45-49), the particulate media (40) allowsfor efficient thermal communication by maximizing surface-to-surfacecontact between the pellets (40) and both the introduced specimenvessel(s) (50) as well as the thermal element (32).

Although oblong pellets (40) according to some aspects of the presentinvention may have a widest dimension (w) as large as thirtymillimeters, the bulk of the pellets (40) of the most preferredembodiment have widest dimensions (w) of less than ten millimeters andpreferably more than two millimeters.

In practice, in order to manage costs, the thermally-conductive pellets(40) of preferred embodiments are formed from irregularly-shapedparticles of raw material, preferably with rounded and smooth surfaces.Even though such raw material is available with fairly smooth surfacesin its raw state, for optimal use of the present invention, it should bepolished smooth in order to minimize friction between adjacent pellets(40) in a bath system (20). Pellets (40) are made of thermallyconductive raw material, preferably a solid metal and most preferablyaluminum or an aluminum alloy. Such raw material is preferably acquiredfrom metal manufacturing plants in the form of pellets or shot, whichmay also be referred to as “granny pea,” “mini pea” or “granulatedparticle ingot,” and can be obtained at high purity, preferably ofgreater than 99% purity. The raw material is preferably not molded, inorder to minimize cost of manufacture and/or purchase. Any standardsmall metal parts finishing equipment such as a vibratory bowl orvibratory tub can be used to polish the raw material with or withoutabrasives to achieve the desired polished surface characteristics of thepreferred embodiments.

The performance characteristics of the resulting thermally-conductivepellets (40) are favorable attributes of the preferred embodiments. Notonly do the resulting pellets (40) allow for high thermal conductivityand thermal retention when used in system (20), but pellets (40) alsoprovide a balance of mechanical fluidity and support. The balance ofmechanical fluidity and support allows vessels (50) to be readilyinserted into the particulate media (40) [or the multi-phase media (71),when used in any particular embodiment] and thereafter held in place ina static position due to the mechanical interaction between theparticulate media (40). A favorable aspect of the particulate media (40)resulting from this preferred method is that the bulk (i.e., themajority by volume) of the pellets are oblong in shape, which enhancesthe overall fluidity of the resulting media (40). Moreover, the pellets(40) of preferred embodiments are microbial resistant and are bothmoisture and gas impermeable.

Although some embodiments use pellets (40) of uniform sizes, otherpreferred embodiments use pellets (40) of mixed sizes and shapes, whichtypically allows for improved fluidity and thermal conductivity due tothe distribution of smaller pellets with respect to larger pellets in amixture. Irregularly shaped thermally-conductive pellets (40) preferablyhave widest dimensions (w) in the range of 2-10 millimeters andpreferably take on an overall form of smooth symmetrical ornonsymmetrical ellipsoids, such as in a blend from which the fiverepresentative samples of FIGS. 6 & 7 have been sampled.

Despite the general preference to use rounded pellets that have beenpolished smooth, some aspects of the invention may still be appreciatedwith less-preferred alternative forms for pellets (40), that may includerough, jagged, uneven, rutted, bumpy, pitted, and etched forms,including polygons such as cubes, cones, pyramids, and cylinders, ortwists, or rings, or various combinations of these or other forms.

FIG. 8 shows a solid, homogenous pellet (41) as a representativecomparator for any of the solid, homogenous pellets (40-49) describedabove with reference to FIGS. 1-8. As a homogenous pellet (41), theouter surface (41 a) is of the same composition as the core (41 b) ofthe pellet (41) shown in FIG. 8, the composition beingthermally-conductive and preferably a solid metal. The specificcomposition of the thermally-conductive material in preferredembodiments is most preferably aluminum or an alloy of aluminum. Inalternative embodiments, copper, graphite, cobalt oxide or otherthermally-conductive materials may alternately be used as thethermally-conductive raw material for pellets (40), as will be known tothose of skill in the art. Alternative materials such as lightweightthermally-conductive plastics, epoxies and the like are particularlyadvantageous alternatives for use in applications where either minimalweight is desired and/or where there is a desire to minimize electricalconductivity through the particulate thermal media (40) within tub (30).

With reference to FIGS. 9 & 10, certain additional advantages areobtained with alternative embodiments that employ pellets (40) havinghollow and/or differential composition, respectively. FIG. 9 moreparticularly shows a representative thermally-conductive pellet (41)having a thermally conductive outer surface (41 a′) surrounding asubstantially hollow core (41 b′). FIG. 10 shows a representativethermally-conductive pellet (41) having a thermally conductive outersurface (41 a″) surrounding a less dense or less conductive core (41b″). The outer surface (41 a″) can be made from any sufficientlythermally-conductive material and is composed of a different materialthan the material of inner core (41 b″), which can be made from anyrigid or non-rigid material such as ceramic, plastic, foam, water, gelor other semi-liquid or liquid. Due to the difference between thethermal conductivity and/or density properties of the surface (41 a″)and the core (41 b″) of representative pellet (41″), pellet (41″) isreferred to as having “differential composition”. As will be understoodby those of skill in the art, any of the variously shaped pellets(40-49) described in this application can be made of hollow ordifferential composition just as pellet (41′) is hollow and pellet (41″)has differential composition.

With reference again to FIG. 1, in some preferred embodiments, tub (30)is filled with a multi-phase media (71), which is a multi-phasevariation of thermally-conductive media. Multi-phase media (71) is“multi-phase” in that it is a combination of particulate media (40) anda fluid (70), preferably a liquid. Alternate embodiments of the fluid(70) of multi-phase media (71) include semi-liquids, gasses or vapors,or combinations thereof or combinations with liquids. Preferably,though, multi-phase media (71) includes particulate thermal media (40)[most preferably like oblong pellets (45-49)] together with water orother liquid media (70). In such embodiments, the fluid media (70) isgenerally included to help enhance the thermal properties of the thermalmedia (71). Liquid media (70) may also consist of or include lubricantsand/or disinfectants (or the like) for the purposes of increasingfluidity and microbial control, respectively, of the media (71) withintub (30).

With embodiments relating to multi-phase media (71) that include liquidfluid media (70), the liquid portion (70) of the thermal media (71)generally fills the interstitial spaces (40′) between the pellets (40),at least up to the level of the upper surface (70′) of liquid media(70). For embodiments with liquid media (70), the level of the uppersurface (referred to as the “fill level”) (70′) of liquid media (70)preferably covers substantially all of the particulate media (40), suchas illustrated in FIG. 1. However, lower liquid fill levels may also beused as desired. For instance, the fill level of liquid media (70) canbe limited to a low level (70″) (shown in dashed line) that covers thethermal element 32 but does not cover all the particulate media (40). Atsuch a low fill level (70″), thermally-conductive liquid fluid media(70) helps facilitate heat transfer between thermal element (32) andparticulate media (40) without wetting as much of the particulate media(40) and/or the specimen vessel(s) (50).

Although not essential to all aspects of the present invention, somepreferred embodiments also utilize an impeller (75) (or a tumbler or thelike) to stir or agitate the beads (40) and cause them to be spaciallyredistributed within tub (30), thereby increasing the rate of heattransfer within media (40) relative to thermal source (32). Operation ofimpeller (75) is especially beneficial to rapidly change (or “ramp up”or “boost”) the temperature of the particulate media (40) near the topof tub (30), such as may be desired during prep time before vessels (50)are placed in media (40). However, as is shown in FIG. 1, impeller (75)is preferably disposed at a position within tub (30) such that impeller(75) is not likely to physically engage vessel(s) (50) during itsoperation. As a substitute or augmentation for impeller (75),alternative devices or systems for stirring or otherwise spaciallyredistributing pellets (40) and/or for rapidly boosting or changing thetemperature of particulate media (40) will be evident to those of skillin the art. A heated air blower (such as a hair blow dryer) positionedto blow through the media (40) is one particular example of such analternative embodiment for use to rapidly boost the temperature ofparticulate media (40), particularly for when media (40) is used dry.Systems for circulating super-heated steam through dry particulate media(40) can also be used to serve both the boost function as well as thesterilization purpose described elsewhere herein. Although not shown inFIG. 1, those of ordinary skill in the art will understand that impeller(75) (or its alternatives or equivalents) has an associated motor andmotor controls for turning the shaft (76) to operatively rotate impeller(75).

Despite the benefits of such multi-phase media (71), other aspects ofthe present invention can be appreciated without using any fluid portion(70) of the thermal media in tub (30), in which cases the particulatemedia (40) is dry particulate media. By using dry particulate media(40), many of the hazards and maintenance burdens of using water bathscan be avoided.

While numerous variations on the size, shape and composition of theparticulate media (40) and/or multi-phase media (71) have been describedabove, it should be understood by those skilled in the art having thebenefit of this disclosure that the drawings and detailed descriptionherein are to be regarded in an illustrative rather than a restrictivemanner, and are not intended to limit the invention to the particularforms and examples disclosed. On the contrary, the invention includesany further modifications, changes, rearrangements, substitutions,alternatives, design choices, and embodiments apparent to those ofordinary skill in the art, without departing from the spirit and scopeof this invention, as defined by the claims that may appear with thisapplication or may be later added or amended. Thus, although theforegoing embodiments have been described, those of ordinary skill inthe art will recognize many possible additional alternatives. Forexample, although it is preferred that at least the bulk of theparticulate media (40) consist of a blend or mixture of one or more ofthe embodiments described herein, it may be beneficial to useparticulate media (40) and/or multi-phase media (71) that includesblends or mixtures of the various embodiments that have been describedtogether with other materials that have not been remotely described oreven suggested. In any case, all substantially equivalent forms ofparticulate thermal media should be considered within the scope of thethermal media of this invention to the extent that the claims do notpreclude as much when properly construed.

While much of the above descriptions describe preferred forms ofparticulate media (40) and production and preparation of the same, FIG.11 shows a flow chart of a preferred process of using thethermally-conductive particulate media (40) in a bath system (20) ofcertain preferred embodiments of the present invention. The first step(81) of such process is to prepare the thermal bath system (20) inaccordance with the foregoing descriptions, filling tub (30) withappropriate particulate thermally-conductive media (40) or multi-phasemedia (71) to the desired fill levels. After preparing and/or obtaininga thermal bath system (20) with thermally-conductive pellets (40) ofappropriate character according to the teachings of the presentinvention, a user (or an automated control) would then proceed to thefollowing steps (82-86).

Referring to the flow chart in FIG. 11, the second step (82) of thepreferred process involves setting the system (20) to the desiredtemperature and activating the thermal controls to maintain as much,thereby bringing the thermal media within tub (30) to the desiredtemperature, whether it be above or below ambient. Such setting andactivating step (82) involves use of thermal source (32), power source(34), and temperature control unit (36) in the conventional manner, withthe aid of thermal insulation (38). To shorten the time to reach thedesired temperature, it may be appropriate to stir the particulate media(40) after 10-30 min and/or periodically. Once stirred, the temperatureof the particulate media (40) should be allowed to equilibrate for 15-60minutes.

The next step (83) of positioning sample vessel(s) (50) in the thermalmedia (40, 71) is generally performed manually and is enabled by thefluidity of the particulate media (40). As is conventional with waterbaths, the objects or specimen vessel(s) (50) should be placed such thatthey are substantially immersed in media (40) without being immersed sofar as to risk contamination through any upper opening in the vessel(s)(50), particularly when a liquid (70) is used with particulate media(40). Once appropriately placed, the vessel(s) (or objects) (50) canthen remain in place without a rack and are left to incubate (i.e., toremain at the set temperature) for whatever period of time is desired.After the desired incubation time has been achieved, the vessel(s) (50)are removed (typically by hand) from system (20) at the bottom step (85)for further processing outside of system (20).

The final step (86) before reusing the system (20) is to clean orsterilize the thermally conductive media (40, 71) using techniquesmentioned elsewhere herein or as will be evident to those of skill inthe art. The final step (86) also preferably involves briefly agitatingthe particulate media (40) both after the last use and before the nextuse of system (20). While this step (86) is shown serially between thesample removal step (85) and the restart step (82), it should beunderstood that sterilization (86) (and other steps) may be omittedentirely or may be performed in a different sequence. This isparticularly the case with the sterilization and/or cleaning step (86)as alternative cleaning and/or sterilization processes may be performedduring the course of other steps (81-85) of the process, or may beomitted entirely, to the extent that bioburdens within media (40) arewithin levels required for integrity of whatever test is being conductedon vessel(s) (50).

In a particularly preferred variation of the thermal bath system (20)shown in FIG. 1, programming controls are included with temperaturecontrol unit (36) to also control the staged and timed operation of eachstep (81-86) of the method of FIG. 11. In such variation, control unit(36) includes one or more timers to automatically activate parts ofsteps (81-86) at scheduled or anticipated times during the day andduring each cycle of using system (20). Particularly, automated cleaningand/or sterilizing variations of step (86) are automatically activatedby control unit (36) at scheduled times after and before each shift inwhich the thermal bath system (20) has been or is likely to be used, inorder to minimize microbial contamination in tub (30). Likewise, thethermal source (32) and/or the impeller (75) are activated by controlunit (36) at scheduled or anticipated times before each shift in whichthe thermal bath system (20) is likely to be used, in order to minimizecostly staff and/or equipment downtime (and potentially costly waste ofspecimens) while waiting for the required temperature of media (40) tobe reached. Once the required temperature of media (40) is attained, asdetermined by a temperature probe or the like connected to control unit(36), automated controls in unit (36) then preferably deactivateimpeller (75) and cause a visual, auditory or electronic “READY” signalto be presented to users of system (20). Thereafter, thermal controlscontinue to maintain the temperatures in the conventional manner,allowing for a user to program the duration of the incubation time (orthe remaining incubation time) or to adjust the temperature setting ofcontrol unit (36) to any particular level at any time. Once theprogrammed incubation time is completed, the automated controls of unit(36) preferably also include provision for presenting an “INCUBATIONCOMPLETE” visual, auditory or electronic signal to indicate that thedesired incubation period is completed, while also discontinuingoperation of thermal source (32) at the appropriate time.

In certain embodiments, such automated controls of control unit (36) mayalso be coupled to automated specimen racks in order to cause vessel(s)(50) to be inserted into and/or removed from media (40) in accordancewith a pre-programmed sequence, in order to provide a fully automatedsystem (20).

In broad embodiment, the present invention is thermal bath media ofthermally-conductive particulate media of any shape or material whichcan be used to replace conventional wet or dry media in existinglaboratory thermal bath for transferring thermal energy to objectsplaced within. The present invention also envisions laboratory thermalbath optimally designed for use with thermally-conductive particulatemedia. Such laboratory thermal baths can comprise tub designs thatprovide optimal containment of the thermal bath media, optimal thermaltransfer properties, and optimal design for ease-of-use, adaptation torobotic platforms and sterile laboratory applications.

While the foregoing written description enables one of ordinary skill tomake and use what is considered presently to be the best mode thereof,those of ordinary skill will understand and appreciate the existence ofvariations, combinations, and equivalents of the specific embodiment,method, and examples herein. The invention should therefore not belimited by the above described embodiment, method, and examples, but byall embodiments and methods within the scope and spirit of the inventionas claimed. It is intended instead that any claims with thisapplication, or any claims that may be added or amended, be interpretedto embrace all further modifications, changes, rearrangements,substitutions, alternatives, design choices, and embodiments that may beevident to those of skill in the art. Although the foregoing embodimentsare the most preferred at present, those of ordinary skill in the artwill recognize many possible alternatives. For example, it may bepossible to find another material that works better than the particularswe have discussed. In any case, all substantially equivalent systems,articles and methods should be considered within the scope of thepresent invention.

1. A thermal bath medium for laboratory use capable of maintaining arelatively constant temperature, said medium comprising a plurality ofpellets having a thermally-conductive composition.
 2. The medium ofclaim 1, wherein the plurality of pellets comprises aluminum.
 3. Themedium of claim 1, wherein the plurality of pellets comprises copper. 4.The medium of claim 1, wherein the plurality of pellets comprisessilver.
 5. The medium of claim 1, wherein the plurality of pelletscomprises a carbon polymer.
 6. The medium of claim 1, wherein theplurality of pellets comprises a plastic polymer.
 7. The medium of claim1, wherein the majority of the plurality of pellets are shaped such thatat least one cross-section of the pellets is non-circular.
 8. Thepellets of claim 7, wherein the media comprises pellets having asubstantially irregular shape.
 9. The pellets of claim 7, wherein themedia comprises pellets having a mixture of uniform shapes and sizes.10. The pellets of claim 7, wherein the media comprises pellets having amixture of different shapes and sizes.
 11. The pellets of claim 7,wherein the media comprises pellets having a smooth and hardenedsurface.
 12. The pellets of claim 7, wherein the media comprises pelletsimpermeable to moisture and gases.
 13. The pellets of claim 7, whereinthe media comprises pellets having a substantially small size of lessthan thirty millimeters in diameter.
 14. The pellets of claim 7, whereinthe pellets comprise an outer surface and a core, wherein the thermalconductivity of the core is distinguished from the thermal conductivityof the surface.
 15. The pellets of claim 7, wherein the core is hollow.16. The pellets of claim 7, wherein the surface is permanently coatedwith antimicrobial agent.
 17. The pellets of claim 16, wherein theantimicrobial agent comprises ionic silver.
 18. The pellets of claim 16,wherein the antimicrobial agent comprises ionic copper.
 19. The pelletsof claim 16, wherein the antimicrobial agent comprises a bactericide.20. The pellets of claim 16, wherein the antimicrobial agent comprises afungicide.
 21. The pellets of claim 16, wherein the antimicrobial agentcomprises an algaecide
 22. The pellets of claim 16, wherein theantimicrobial agent comprises an virucide
 23. A thermal control systemfor controlling the temperature of a sample in a vessel, comprising: alaboratory thermal bath having a tub and a thermal source;thermally-conductive media comprising thermally-conductive pelletswithin said tub in thermal communication with said thermal source; andthermally-conductive media being positioned in said tub in a manner suchthat sample vessels can be inserted within the media in thermalcommunication with the media.
 24. The thermal control system of claim23, further comprising a supply of antimicrobial compound fordecontaminating the surface of the pellets.
 25. The thermal controlsystem of claim 24, wherein the antimicrobial compound comprises aliquid periodically applied to the surface of the pellets.
 26. Theantimicrobial compound of claim 25, wherein the liquid comprises silver.27. The antimicrobial compound of claim 25, wherein the liquid comprisesammonium.
 28. The antimicrobial compound of claim 25, wherein the liquidcomprises alcohol.
 29. The antimicrobial compound of claim 25, whereinthe liquid comprises chlorine.
 30. A method for controlling thetemperature of a specimen, comprising the steps of filling a thermalbath with thermally-conductive pellets, placing the specimen in thepellets after bringing the pellets to a desired temperature, andincubate the specimen for a desired period of time.